A fiber optic cable contains multiple, mutually-isolated, coated glass fibers. Sometimes the fibers in one cable are not identical in each of their diameters to the fibers in a second cable. Different optical fibers that meet different performance standards may not be identically manufactured which may result in slightly different optical fiber diameters. Different standard specifications for optical fibers are published by the International Telecommunication Union-Telecommunication Standardization Sector (ITU-T). These specifications vary from the ITU-T G.652 specification to the ITU-T G.657 specification, with some eighteen or more specifications or sub-specifications in between which may result in optical fiber diameter variations.
A mismatch in diameter between two optical fibers, for any reason, can result in significant insertion loss (signal loss) at a splice junction between the two optical fibers if their cross-sections at the splice junction do not optimally overlap. Even small variations in diameters on the order of 10% can be problematic. Consequently, when splicing optical fibers with different diameters, for example, by technicians working on a fiber optic cable installation at a construction site of a multi-dwelling unit (MDU), the technicians try to align the fibers optimally to mitigate insertion loss at the splice junction.
Different splicing techniques offer different alignment capabilities. For example, a fusion splicer can make use of photonics for alignment purposes, and thereby achieve a mode-field diameter alignment, a fiber-core alignment or a fiber cladding alignment, each of which probably provides a better overlap between the spliced optical fibers' cross sections as compared with the overlap achievable by a mechanical splicer. The mechanical splicer generally can not align two fibers as well as a fusion splicer because it is limited to geometrical/mechanical alignment constraints only.
But, a mechanical splicing technique has advantages; it is much less costly and easier to use than a fusion splicing technique. The latter requires a relatively expensive splicing instrument, access to electrical power which is sometimes not readily available during initial phases of building construction, more highly trained technicians, and more money for repairs if the fusion splicer is dropped or otherwise damaged during use. In a cable installation for a multi-dwelling unit (MDU) such as a large apartment building, the large number of required splices makes fusion splicing cost prohibitive. For that reason, and because of the other factors noted above, it would be preferable to use mechanical splicing, provided that misalignments resulting from mechanical splicing of optical fibers with unequal diameters could be mitigated.
There are different kinds of mechanical splicers, but a current widespread design uses a “V” groove as a channel to hold two optical fibers to be spliced together. The walls of the V groove are flat, and a cover pressing down on top of the open V channel presses against at least the larger of two unequally-diametered fibers. Because of geometry and gravitational force, the smaller diameter optical fiber is displaced downward in the direction of the bottom of the V channel, relative to the supported location of the larger diameter fiber. Thus, there is non-concentric overlap between the cross-sections of these two fibers at their splice junction, as a function of diameter difference. A portion of the cross-section of the smaller fiber hangs below the bottom of the cross-section of the larger fiber, or if the portable splicer is momentarily rotated by the technician on the job site for whatever reason, where either of the normally-up corners of the V-channel is momentarily located in a down position, a like portion of the cross-section of the smaller fiber could then protrude beyond the periphery of the larger fiber in the direction of that momentarily down corner.
Applicant provides an improvement to this V groove mechanical splice design by moving the cross-sections towards concentricity and thereby achieving increased cross sectional overlap and reduced insertion loss. Insertion loss has been reduced by as much as 0.1 dB-0.2 dB from use of Applicant's improvement, which shall be appreciated as being significant by those of skill in the art.